When the heart relaxes blood is pulled back from the cavities through small valved openings along its length.

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Heart and circulation

Closed circulatory system

Blood is enclosed within tubes so it is at higher pressure. Consequently it travels faster and is therfore more efficient to meet the requirements of organisms with a large surface area to volume ratio (multicellular).

Blood leaves the heart under high pressure before flowing from the arteries>arterioles> capillaries>venules>veins.

Capillaries are close to cells to allow substance exchange.

Blood then returns to the heart.

There is 2 types of circulatory system:single and double.

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Single and double circulatory systems

Single circulatory system

The heart pumps deoxygenated blood under high pressure to the (gills) where diffusion/gas exchange takes place.

The oxygenated blood then leaves the gills and flows around the body before returning to the heart.

Double circulatory system

The right ventricle pumps deoxygenated blood to the lungs to receive oxygen.

The oxygenated blood returns to the heart where the left ventricle pumps the blood to the rest of the body.

This allows the system to maintain efficiency through a high metabolic rate

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The transport medium

Plasma is comprised of water and dissolved substances (carbon dioxide, oxygen and food/glucose).

It transports: proteins, urea, salts and antibodies.

RBC,WBC, and platelets are carried in the blood.

It helps regulate temperature.

Water : A small polar molecule (uneven distribution of charge) , H+/O-, hydrogen bonding (H+ attracted to O- on other molecules, this makes water a liquid), chemicals dissolve in it easily (for biochemical reactions in the cytoplasm), ionic compounds become hydrated as Na+ is attracted to the O- and Cl- is attracted to the H+ ultimately causing separation, cells react with the water to carry out condensation and hydrolysis reactions, it has a high specific heat capacity (large amount of energy input only causes a small rise in temperature which helps avoid rapid internal changes.

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Heart and blood vessels

To heart

Pulmonary vein (oxygenated from lungs)

Vena cava (deoxygenated blood from arms, head and lower body)

Away from heart

Aorta (main transporter, oxygenated blood to the body)

Pulmonary artery (deoxygenated blood to the lungs)

Atrioventricular valves prevent backflow of blood into the atria.

Semilunar valves prevent backflow of blood into the ventricles

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Comparison between arteries/veins/capillaries

Arteries: Narrow lumen, thick walls , more collagen, elastic fibres and smooth muscle, and they have no valves.

Veins: Wide lumen, less collagen, elastic fibres and smooth muscle, thin walls and they have valves.

Capillaries: One cell thick, and 10 microns in diameter.

Elastic fibres are needed for stretch and recoil.

Collagen is needed to form a rigid and durable structure.

Smooth muscle is needed for constriction and dilation.

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How does blood move through vessels?

Systole- blood is forced into the arteries which stretch to accomodate the blood.

Diastole-blood propelled forward due to stretch and recoil of the artery wall behind the blood (pulse).

When blood reaches the arterioles and capillaries there is a steady flow of blood which allows exchange of substances in the capillaries between the blood and surrounding cells (rapid diffusion) .

In the veins blood flow is assisted by skeletal muscle contractions and breathing.

Breathing causes low pressure in the thorax which draws blood back in to the heart.

Valves prevent backflow.

The heart can't directly use the blood in its chambers so the heart muscle is supplied with blood from the coronary arteries

Oedema

Arterial end of the capillary blood is under high pressure which forces fluid and small molecules found in the plasma out of the capillaries into intercellular spaces, forming tissue fluid.

The capillary walls only allow small molecules through (not proteins or blood cells)

If blood pressure is raised more fluid may be forced out of the capillaries causing fluid accumulation and oedema.

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Dietary factors

Carbohydrates, lipids and proteins all store energy,

(Least energy) carbohydrates->proteins->alcohol->lipids (most energy)

calorie is the quantity of heat energy required to raise the temperature of 1 cm^3 of water by 1 degree.

1 kilocalorie=1000 calories

1000 calories = 1 Calorie

1 calorie=4.18 joules

Energy content of foods is measure in joules (j) (1 Kj=1000j)

Turn 2000 kj into calories and Calories

2000 kj=2000000j

2000000/4.18 = 478468.8995 calories

478468.8995/1000=478 Calories

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Carbohydrates

Cx(H20)n

Monosaccharide is a single sugar unit. It is a rapid source of energy which causes a sharp rise in blood pressure.

Disaccharide is 2 sugar units joined together by condensation reaction to form a glycosidic bond.

Long straight, or branched chains form polysaccharides.

Monomer is an identical or similar subunit.

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Monosaccharide

(CH20)n (n= number of carbons)

They have between 3 and 7 carbons.

Most have 6 carbons and are called hexose sugars (glucose, galactose and fructose)

Hexose is a ring structure.

Glucose= respiration

Galactose=milk

Fructose=seed dispersal and dieting

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Disaccharide

2 single sugar units joined together by a condensation reaction to form a glycosidic bond (which can be split by hydrolisis).

A water molecule is released.

Some examples are: sucrose, maltose and lactose.

Sucrose= fructose and glucose (form of sugar transported in a plant)

Maltose=glucose and glucose (formed when amylase breaks down starch)

Lactose=glucose and galactose (used in milk, hydrolyse lactose to give glucose and galactoseto give more tolerance)

Polysaccharides and disaccharides must be broken down into monosaccharides before being absorbed. Monosaccharides are released slowly so don't cause swings in blood pressure like eating monosaccharides.

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Polysaccharide

Polymers made from simple sugar monomers, joined by glycosidic links into long chains)

Cholesterol

Cholesterol isn't soluble in water so for it to be transported it combines with proteins to form lipoproteins.

LDLs Low density lipoproteins: main cholesterol carrier in the blood. Saturated triglycerides + protein + cholesterol. They bind to receptor sites on cell membranes excess LDLs overload these receptors so there is high blood cholesterol levels that can be deposited in artery walls forming atheromas.

HDLs High density lipoproteins: Higher percentage of protein. Unsaturated triglycerides+cholesterol+proteins. They transport cholesterol to the liver to be broken down which lowers blood cholesterol levels and helps remove fatty plaques.

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Smoking/Inactivity

Smoking

Haemoglobin carries carbon monoxide instead of oxygen so less oxygen is reaching the cells . When arteries narrow blood supply further there is even less oxygen reaching the cells which results in an increased heart rate .

Nicotine stimulates the production of adrenaline which causes blood vessels to constrict which increases blood pressure.

Carcinogens can cause endothelial damage.

It reduces HDL levels.

Inactivity

Exercise maintains a healthy weight, reduces the risk of obesity and hence the development of tye 2 diabetes , increases HDL levels without affecting LDLs.

An active person is more likely to survive a heart attack or stroke.

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Heredity and risk/apolipoproteins

Heredity and risk

Some single gene disorders increase early development of CHD.

FH (familial hypercholesterolaemia) leads to mutations in the LDLR gene which causes LDL receptors to not form or to be defective which results in high blood LDL levels.

Apolipoproteins (protein component of lipoproteins, formed in the liver and intestines, helps stabilise lipoprotein structure)